1. Field of the Invention
The present invention relates to a spar-buoy boring derrick for a sea-bottom drilling scaffold which is used for sea-bottom geological survey or boring, etc.
2. Prior Art
In a sea-bottom geological survey or boring work in a relatively shallow area, piles are driven into the sea-bottom, or scaffold piping is assembled onto which a deck is fastened to be used as a scaffold. Also, single column steel pipes are installed straight up on the sea-bottom with their neck moored to anchors on the sea-bottom using mooring ropes. Another method was to lower three or more spuds onto the sea-bottom and pull a hull to the sea level to be used as a scaffold. In a deep area, a steel scaffold derrick was used for a boring scaffold.
Among these methods, the method using a steel scaffold required either a lot of time and effort to move or a large scale facility in order to bore at a prescribed interval, resulting in a huge cost.